Furnace



April 1936- H. c. FREN/TZEL, JR 2,037,970

FURNACE Filed July 19, 1934 3 Sheets-Sheet l INVENTOR.

33 v B? 2M1) ATTORNEY.

April 14, 19 6- H. c. FRENTZEL, JR

FURNACE I Filed July 19, 1934 3 Sheets-Sheet 2 INVENTOR.

ATTORNEY.

A ril 14, 1936. 2,037,070

H. C. FR ENTZEL, JR

FURNACE Filed July 19, 1954 s Sheets-Sheet s 39L 7) R zil.

- i i/a4 ATTORNEYzfS.

Patented Apr. 14, 1936 PATENT OFFICE FURNACE Herman C. Frentzel, Jr., Milwaukee, Wis., as-. signor to The Hell 00., Milwaukee, Wis., a corporation of Wisconsin Application July 19, 1934, Serial No. 735,921

2 Claims.

The present invention relates in general to improvements in the art of heating, and relates more specifically to various improvements in the construction and operation of hot air furnaces especially adapted for cooperation with oil burners or the like.

Generally stated, the primary object of the pres ent invention is to provide an improved hot air furnace which is simple in construction and highly eliicient in operation.

Numerous types and styles of hot air furnaces have heretofore been employed for domestic heating purposes, and some of these prior heaters have been relatively satisfactory and successful when coal was utilized as the heating fuel. With the use of coal beds and grates in furnaces of this kind, relatively short and few heat transfer surfaces could be utilized to produce quite satisfactory heating of the air, without waste of heat due to excessively high temperature of the stack gases. But when it is attempted to operate such prior coal-burning furnaces with intermittently operable oil burners or the like, wherein relatively intense heat is generated within or closely adjacent to the combustion chamber of the heater, the heat transfer surfaces are entirely inadequate both in area and in length to cause efi'ective absorption of the available heat from the gases of combustion traveling at relatively high velocity and to prevent excessive waste thru overheated stack gases.

It is therefore a more specific object of the present invention to provide an improved hot air furnace which is especially adapted to cooperate with an oil burner or similar heating source in a manner whereby maximum efficiency and most effective heat transfer are obtainable.

Another specific object of the invention is to provide an improved furnace structure which is simple, compact, and durable in construction, and which may be readily assembled or dismantled fo convenient transportation.

Still another specific object of the invention is to provide an improved heat transfer device wherein possible leakage of combustion gases into the spaces occupied by the heat-absorbing medium is positively eliminated.

A further specific object of the invention is to provide a durable and neat-appearing furnace assemblage, which may be manufactured and sold at minimum cost, and which requires least attention during normal use thereof.

These and other specific objects and advantages will be apparent from the following detailed description.

A clear conception of an embodiment of the present invention and of the mode of constructing, of assembling, and of operating a hot air furnace built in accordance with the improvement may be had by referring to the drawings accompanying and forming a part of this specification, in which like reference characters designate the same or similar parts in the various views.

Fig. 1 is a front and side perspective view of the heat transfer portions of one of the improved hot air furnaces, with the outer casing or housin removed;

Fig. 2 is a. longitudinal section thru the side conduits of the heat transfer structure of the improved furnace, taken along the irregular line 2-2 of Fig. 3;

Fig. 3 is a transverse section thru the improved furnace, taken along the line 3-3 of Fig. 4;

Fig. 4 is a central, longitudinal section thru the furnace structure, taken along the line 44 of Fig. 3;

Fig. 5 is a full top view of the heat transfer unit of the improved furnace, showing the outer casing in dot-and-dash lines; and

Fig. 6 is an enlarged, horizontal section thru the joint between several of the sections of the heat transfer unit, the section being taken along the line 66 of Fig. 4.

While the invention has been shown and described herein as being applied to a hot air furnace of definite capacity and having a relatively limited number of gas-conveying conduits and ducts, it should be understood that it is not intended to restrict the scope by such specific embodiment since the novel features are also applicable to furnaces of larger and smaller capacity than that specifically shown.

Referring to the drawings, the improved furnace comprises, in general, an internal heat transfer unit including a central combustion chamber In and ducts associated therewith for confining and for conducting the hot gases of combustion along circuitous paths toward the outlet or stack I I, all of these being shown in full lines; and an outer air-confining casing l2 forming a seal housing for the heat transfer unit, the casing I2 being provided with suitable, lower air inlet and upper air outlet connections communicating therewith at selected places, in a well-known manner and being shown in dot-anddash lines.

The improved heat transfer unit is composed of a main or central section, including the combustion chamber I0, which is located at the forward portion of the central section; and two similar but oppositely facing side sections l3, I4 disposed on opposite sides of the central section and detachably connected to the latter by means of special gas-proof joints such as shown in detail in Fig. 6. The combustion chamber 40 has a combustion zone in the lower portion thereof in horizontal alinement with a nozzle or burnerreceiving opening l5 and has upwardly increasing, cross-sectional area, as clearly shown in Figs. 1 and 3. Both the bottom and the top of conduits I8 communicating therewith thru the rear wall of the chamber I0, and the rear ends of these conduits I8 are in open communication with the upper interior of a transverse casing I9 having a horizontal partition 20 therein, which divides the casing I9 into upper and lower passages 2|, 22 respectively. A stack connection 23 communicates directly with the lower passage 22 and with the stack II but does not communicate directly with the passage 2 I, and the chamber I9, conduits I8, casing I9, partition 20, and connection 23 are formed of heavy and durable sheet metal united as by weldinginto an integral structure which comprises the central section of the heat transfer unit. I

Each of the oppositely facing, detachable side sections I3, I4 of the heat transfer unit comprises a rear casing 24 having a central, horizontal partition 25 therein which is alineable with the central partition 20 of the casing I9 so as to provide continuations or extensions for the passages 2|, 22 within the casings 24. A series of vertically elongated, relatively narrow, horizontal, upper ducts 28 is located at each side of the group of conduits I8 and of the upper portion of the chamber I0, and these ducts 28 connect the ends of the upper passages 2| with the upper portions of the front casings 29. The vertically elongated front casings 29 have their lower portions connected by similar, lower, horizontal ducts 30, with the end portions of the lower passages 22, as shown in Figs. 1 and 2; and the ducts 30 of each lower series are staggered vertically relative to the ducts 29 of the corresponding upper series as illustrated in Fig. 3. The medial, forward portion of each casing 29 is provided with an inspection opening 3| normally closed by a door 32, and the side portion of each rear casing 24 is likewise provided with an inspection opening 33 which is normally covered by a closure 34 as shown in Fig. 5. The combined cross-sectional area of all of the upper ducts 28 is approximately equal to that of all of the lower ducts 30, and is also substantially equal to the combined cross-sectional area of the conduits I8. The rear and frontcasings 24, 29, and the ducts 28, 30 of each side section are again formed of heavy and durable sheet metal united as by welding into an integral structure, and the twoside sections are similar in construction with the exception that the rear casings 24 thereof are reversed. The central and side sections I3, I4 of the improved heat transfer unit are rigidly connected to each other at the rear portion only of the adjacent sections, as shown in Fig. 5, by means of gas-proof detachable joints such as illustrated in detail in Fig. 6. Each of these joints comprises an H-sectioned fitting 35 having oppositely facing recesses within each of which a continuous strip 36 of packing material is disposed; and a series of bolts 31 coacting with lugs 38 secured to the adjacent casings I9, 24 so as to force the ends of these casings toward each other and against the packing strips 36. Any desired number of bolts 31 may be employed, and

the lugs 38, which may be of any desired length, may be welded or otherwise rigidly attached to the casings I9, 24. The several sections of the heat transfer unit may also be provided with supporting legs 39 which are adjustably secured to plates 40 rigidly attached to the chamber I0 and casings I9, 24, 29, by means of clamp-ing nuts 4| so as to provide for proper alinement of the unit. The outer housing or casing I2 may be formed of relatively light sheet metal so that the attachment of the air supply and discharge connections may be readily effected, and this casing may coact either with the inner faces of the flanges at the various inspection openings, as shown, or with the external surfaces of these flanges. As shown in Figs. 3 and 4, the improved furnace may also be provided with a water heating coil 42 which passes thru one of the conduits I8 and into the combustion chamber I0, and the ends of this coil 42 pass thru the rear wall of the casing I9 and thru sealing thimbles 43 connect' ing'the casing I 9 with the outer casing I2.

During normal operation of the improved hot air furnace, and assuming the structure to have been completely assembled, with the outer casing I2 enclosing the heat transfer unit, the fuel oil is injected thru the opening I5 and is ignited. The gases of combustion then travel thru the various chambers, conduits, and ducts substantially as indicated by the arrows in Figs. 2 and 4. The hottest gases of combustion first circulate upwardly thru the combustion chamber I0 and subsequently pass rearwardly thru the vertically elongated conduits I8. Upon reaching the rear casing I9, the hot gases of combustion are diverted laterally thru the passages 2I above the horizontal partitions 20, 25, and into the rear casings 24 of the side sections of the unit. The hot gases of combustion, after passing thru'th'e rear casings 24, advance forwardly thru the upper ducts 28 as indicated in Fig. 2 and are subsequently diverted by the front casings 29 toward the lower ducts 30. The relatively cooler gases advance rearwardly thru the lower ducts 30and ultimately reach the lateral passages 22, wherein they are caused to again travel laterally beneath the partitions 25, 20. Upon passing laterally beneath these horizontal partitions 25, 20 for some distance, the spent gases are eventually delivered thru the connection 23 to the stack I I.

During the time that the heating gases are thus circulating thru the heat transfer unit, cool air is being drawn intothe lower end of the casing and rises along the walls of the combustion chamber I0, ducts 28, 30, casings I9, 24, and conduits I8; and after absorbing heat due to this contacting with the hot conductors, the heated gases are ultimately discharged thru the openin'gs provided at the upper end of the housing casing I2.

Theupward and outward inclination of the side walls of the combustion chamber I 0, provides a laterally widening space which accommodates the upwardly travelling expanding gases of combustion, without excessively increasing the velocity thereof; and these outwardly inclined side Walls also provide ledges which are necessarily engaged by the upwardly flowing external air and tend to retard the velocity of this air. The provision of the relatively long and vertically widened conduits I8 at the rear enlarged portion of the combustion chamber It, forms intervening air passages, and also necessitates horizontal elongation of the side ducts 28, 30 thereby providing a structure having maximum heat transfer surface conflnable within an enclosing casing l2 of minimum size, without undesirably impairing the freedom of circulation of the air through the casing. The staggered arrangement of the upper and lower ducts 28, 30, and the disposition of the lower ducts 28 near the lower portions of the outwardly inclined, side walls of the combustion chamber l0, results in very effective heat transfer, since all of the air must pass in intimate contact with the heated surfaces. The flow of heating gases is, moreover, such that the hottest gases radiate heat to the hottest air by virtue of contacting of the latter with the upper conduits l8 and upper ducts 28, as well as with the upper portion of the combustion chamber Ill. The coolest gases passing thru the lower ducts 30 and thru the lower passages 22 radiate heat to the air at its lowest temperature, thus insuring most effective heat transfer thru-out the furnace. The vertical elongation and lateral narrowing of the conduits l8 and of the ducts 28, 30 provides maximum heat transfer surfaces in a most compact structure, and the improved furnace has proven highly successful in actual commercial operation, especially when cooperating with an oil burner.

By detachably connecting the central and the side sections l3, M at the rear portion of the heat transfer unit only, this unit may be conveniently assembled or dismantled. The legs 39 provide for proper alining of the heat transfer unit and spacing thereof from the floor, and the various closures provided at the openings I5, l6, 3|, and 33 permit convenient access to the interior of the heat transfer unit for any purpose whatsoever. If desired, a water heating coil 42 may be readily applied to the improved furnace structure, and this coil is preferably located in one of the side conduits H! of the series. The improved joint illustrated in Fig. 6 will positively prevent escape of gases of combustion into the air-conducting zone, and by forming the several sections of the heat transfer unit with welded joints thru-out, except at the detachable joints, danger of leakage is entirely eliminated.

From the foregoing description it will be apparent that the present invention provides an extremely simple, compact, and durable hot air furnace which is highly efiicient in operation, especially when fired with an oil burner. The improved furnace'structure may be readily assembled, dismantled, and operated with minimum effort; and when once placed in operation, it is entirely automatic.

It should be understood that it is not desired to limit the invention to the exact details of construction and to the precise mode of operation herein shown and described, for various modifications within the scope of the claims may occur to persons skilled in the art.

It is claimed and described to secure by Letters Patent:

1. In a furnace, a casing forming a vertically elongated and unobstructed combustion chamber and having upwardly and outwardly inclined fiat side walls connected by curved top and bottom walls, means for admitting heating medium longitudinally into the lower forward portion of said chamber, a series of rear ducts extending horizontally away from the rear upper portion of said chamber and having flat side walls forming parallel vertically elongated narrow air passages,

a rear upper header communicating with the rear ends of said ducts and extending laterally thereof beyond the adjacent side wall of said cham-' her, a series of upper side ducts of greater length than said rear ducts extending forwardly away from said rear upper header and along the upper portion of said adjacent chamber side wall and having fiat side walls forming parallel vertically elongated narrow upper side air passages, a front header communicating with the front ends of said upper ducts and extending downwardly therefrom flush with the front end of said casing, a series of lower side ducts of the same length as said upper side ducts extending rearwardly away from the lower portion of said front header and along the lower portion of said adjacent chamber side wall and having flat sidewalls forming parallel vertically elongated narrow lower air passages which are staggered vertically relative to said upper side passages, a rear lower header communicating with the rear ends of said lower side ducts and extending laterally therefrom beneath said rear upper header, said lower side duct series being located nearer the central axis of said chamber than said upper side duct series but substantially the same distance from said adjacent inclined chamber side wall, and a housing enclosing said casing, ducts and headers.

2. In a furnace, a casing forming a vertically elongated and unobstructed combustion chamber and having upwardly and outwardly inclined flat side walls connected by curved top and bottom walls, means for admitting heating medium longitudinally into the lower forward portion of said chamber, a series of rear central ducts extending horizontally away from the rear upper portion of said chamber and having flat side walls forming parallel vertically elongated narrow air passages, a pair of rear upper headers communicating with the rear ends of said ducts and extending laterally thereof beyond the adjacent side wall of said chamber. in opposite directions, a series of upper side ducts of greater length than said rear ducts extending forwardly away from each of said rear upper headers and along the upper portion of the adjacent of said chamber side walls and having flat side walls forming parallel vertically elongated narrow upper side air passage, a front header communicating with the front ends of each of said upper side ducts series and extending downwardly therefrom flush with the front end of said casing, a series of lower side ducts of the same length as said upper side ducts extending rearwardly away from the lower portion of each of said front headers and along the lower portion of the adjacent chamber side wall and having flat side walls forming parallel vertically elongated narrow lower air passages which are staggered vertically relative to the adjacent upper side passages, a rear lower header communicating with the rear ends of each of said lower side duct series and extending laterally therefrom beneath the adjacent rear upper header, said lower side duct series being located nearer the central axis of said chamber than said upper side duct series but substantially the same distance from the adjacent inclined chamber side wall, and a housing enclosing said casing, ducts and headers.

HERMAN Q'F'RENTzEL, JR. 

